1. Field of the Invention
The present invention relates to a medical device for placing an occlusion device within a vessel and more particularly, relates to a vascular catheter-based embolization system which is used to restrict or block the flow of blood through a vessel.
2. Description of the Prior Art
For many years flexible catheters have been used to place various devices within the vessels of the human body. Such devices include dilatation balloons, radiopaque fluids, liquid medications and various types of occlusion devices such as balloons and embolic coils. Examples of such catheter devices are disclosed in U.S. Pat. No. 5,108,407, entitled, xe2x80x9cA Method And Apparatus For Placement Of An Embolic Coilxe2x80x9d; U.S. Pat. No. 5,122,136, entitled, xe2x80x9cEndovascular Electrolytically Detachable Guidewire Tip For The Electroformation Of Thrombus In Arteries, Veins, Aneurysms, Vascular Malformations And Arteriovenous Fistulas.xe2x80x9d Still other examples of embolic coil or stent delivery devices which in these cases incorporate hydraulic fluid delivery systems, are disclosed in co-pending U.S. patent application Ser. Nos. 09/177,848, entitled xe2x80x9cEmbolic Coil Hydraulic Deployment System,xe2x80x9d filed on Oct. 22, 1998 and U.S. patent application Ser. No. 09/382,967, entitled xe2x80x9cHydraulic Stent Deployment System,xe2x80x9d filed on Aug. 25, 1999, assigned to the same assignee as the subject patent application, and are hereby incorporated by reference. All of these patents disclose devices for delivering an embolic device or stent to a preselected position within a vessel of the human body in order to either occlude a blood vessel or to reinforce the walls of a vessel.
In order to occlude a blood vessel by using embolic coils there is usually the requirement that many coils be placed in a single location, and the coils must remain in the position where placed so that thrombus from the blood may form on the coils in order to seal, or partially seal, the space between turns of the coils and the space between coils.
Also, stents have been placed in vessels to prevent restenosis of vessels, or alternatively, to anchor or support fabric mounted on the periphery of the stent to reinforce the walls of a blood vessel.
Such stents which may take the form of a helically wound wire, or tubular-like structures with numerous patterns defining the walls of the device. Examples of various stent configurations are disclosed in U.S. Pat. No. 4,512,338, entitled, xe2x80x9cProcess For Restoring Patentcy To Body Vesselsxe2x80x9d; U.S. Pat. No. 5,551,954, entitled, xe2x80x9cBiodegradable Drug Delivery Vascular Stentxe2x80x9d; and U.S. Pat. No. 4,994,071, entitled, xe2x80x9cBifurcating Stent Apparatus And Method.xe2x80x9d Stents are generally formed of materials that can retain their shape under the pulsatile flow conditions encountered when placed within the body vessel. Some materials that have been used to make stents include metals and alloys, such as, stainless steel, tantalum, a tungsten and nitinol, as well as polymers such as polyvinyl alcohol (PVA), polyglycolic acid (PGA) and collagen.
Numerous procedures have been developed to enable accurate positioning of stents within a vessel. One such procedure utilizes a helically wound wire loop stent with a relaxed diameter. The stent is wound with a smaller diameter while fixing the ends of the stent. This procedure keeps the stent in a small diameter, tightly wound coil. This system is then delivered by the use of a delivery wire through the lumen of a properly positioned catheter. Once the delivery wire is activated to release the stent, the stent radially expands to its relaxed larger diameter. Such a stent positioning apparatus and method is disclosed in U.S. Pat. No. 5,772,668, entitled, xe2x80x9cApparatus For Placing An Endoprosthesis.xe2x80x9d
Another stent positioning system utilizes a self-expanding tubular stent. This stent has a relaxed diameter that approximates the diameter of the vessel to be supported. For transport through the catheter, the stent is positioned on a smaller diameter delivery wire. A sheath is positioned over the stent and delivery wire assembly constraining the stent to a smaller diameter. Once the assembly is placed at the desired location in the vasculature, the sheath is withdrawn exposing the stent allowing the stent to return to its predetermined larger size. The expansion of the stent uncouples the stent from the delivery wire while depositing the stent in the vessel at the desired location.
Another stent positioning system utilizes a radially expandable tubular stent formed of a malleable material. This tubular stent has a predetermined expanded diameter defining a lumen that is approximately the same diameter as the vessel to which the stent will be placed. A balloon catheter is placed within the lumen of the stent and the stent is subsequently compressed to a smaller diameter on top of the balloon portion of the catheter. The assembly is then placed within a properly positioned catheter and delivered to the desired location. Inflating the balloon thereby expanding the diameter of the compressed stent deploys the stent. Once the stent is expanded to its predetermined diameter the balloon is deflated and removed leaving the stent deposited at the desired location.
In accordance with one aspect of the present invention there is provided intravascular embolization device which includes an expandable support element having a relaxed expanded state and a stretched collapsed state, and an embolization element which is mounted on the support element and which serves to substantially prevent the flow of blood through a vessel. More particularly, the support element takes the form of a wire wound in a helical configuration so as to form a plurality of turns when the support element is in its relaxed state and a substantially linear configuration when the support element is in its stretched collapsed state. The embolization element is formed from a flexible elastic material and is attached across one turn of the support element, preferably at the distal end of the support element, so that when the support element is in its relaxed expanded state the embolization element serves to occlude, or partially occlude, a vessel.
In accordance with another aspect of the present invention, the embolization element is formed from a polymer mesh, and preferably from a polyurethane mesh. More particularly, the polyurethane mesh is formed such as to create a plurality of pores each of which have a pore size of about 20 microns.
In accordance with still another aspect of the present invention, the embolization element which is attached to the helically wound expandable support element extends in a plane which is perpendicular to a longitudinal axis of the helically wound support element.
In accordance with still another aspect of the present invention there is provided a vascular occlusive coil deployment system which includes a catheter having a distal section which is formed from a material which exhibits the characteristic that the wall of the distal section of the catheter expands outwardly when fluid pressure is applied within the lumen of the catheter. A deployment system also includes a syringe which is coupled to the proximal section of the catheter for applying a fluid pressure to the lumen of the catheter. In addition, a deployment system includes an intravascular embolization device which includes an expandable support element having a relaxed expanded state and a stretched collapsed state, and an embolization element which is mounted on the support element and which serves to substantially prevent the flow of blood through a vessel. More particularly, the support element takes the form of a wire wound in a helical configuration so as to form a plurality of turns when the support element is in its relaxed state and a substantially linear configuration when the support element is in its stretched collapsed state. The embolization element is formed from a flexible elastic material and is attached across one turn of the support element, preferably at the distal end of the support element, so that when the support element is in its relaxed expanded state the embolization element serves to occlude, or partially occlude, a vessel.